The present invention relates generally to inspection of specimens, such as semiconductor specimens. More specifically, it relates to the analysis of Haze data collected during inspection of bare wafers or wafers that have a uniform film, and the like.
Generally, the industry of semiconductor manufacturing involves highly complex techniques for fabricating integrating circuits using semiconductor materials which are layered and patterned onto a substrate, such as silicon. Due to the large scale of circuit integration and the decreasing size of semiconductor devices, the substrate must be defect free prior to fabrication of the integrated circuits. Thus, inspection procedures for detecting defects, such as particles or scratches, on the bare substrate are therefore critical to maintain quality control. Since the inspection procedures are an integral and significant part of the manufacturing process, the semiconductor industry is constantly seeking to improve the accuracy and efficiency of inspection procedures.
One conventional optical inspection tool for locating defects on bare or unpatterned wafers work by scanning the surface of the bare wafer with a tightly focused laser spot and measuring the amount of light scattered by the illuminated spot on the wafer. One example of such an inspection tool is the Surfscan SP1 DLS and TBI tool available from KLA-Tencor, Inc. of San Jose, Calif.
The incident light may be scattered by defects, such as particles. Thus, one may detect defects by analyzing the light scattered and reflected by the specimen and defects located on the specimen. In addition to gross defects, the surface texture itself produces a certain amount of diffracted light in addition to the light scattered by particle defects. This surface light scatter, commonly referred to as Haze, tends to be concentrated at smaller angles near the specularly reflected light beam. The Haze signal may be analyzed to determine surface roughness. Haze is generally defined as a decrease in the smoothness of a wafer surface from the ideal due to imperfections in the surface, such as, minute steps, contaminants in the grain structure, and other surface defects which cause light scattering or absorption. Subjectively, a wafer surface with a high amount of Haze appears dull while a wafer with little Haze appears glossy. One can then visually inspect the Haze image and generally assess the surface roughness profile.
Although conventional systems for detecting defects work well in certain applications, there is a continuing need for improved inspection apparatus and techniques for facilitating defect detection on bare specimens or specimens having a uniform film layer or stack.